Grasshopper cage data: Effect of Bird Predation on Grasshopper and Plant Communties

This experiment was set up in the same macroplots at Field B E004 that were used in E060. Pairs of 9 m x 9 m plots were demarcated. One plot in each pair was randomly assigned to exclude birds (BEX) and the other to allow birds to forage for grasshoppers in the vegetation (BAL). A frame was built around BEX plots with wooden posts at each corner and heavy aluminum wire stretched between posts 1m above the ground. Bird netting (2.5 cm mesh) was then stretched over this framework and attached to the ground with numerous wire stakes. In 1989, these plots were set up 15 July, but were set up 15 May in 1990 to examine the effects of predation in the early summer. Between 15-25 August, netting was removed and grasshoppers were sampled within both BEX and BAL plots and stored in 70% ethanol for later identification to species or genus, counting and weighing. Grasshoppers were sampled by two people with butterfly nets. After the grasshoppers were sampled, the vegetation was sampled. Within each 9 m x 9 m plot, three 0.1 m x 3 m strips were clipped, sorted to species, dried and weighed. In 1990, the exclosures were set up 15 May, but all vegetation and grasshopper sampling was similar to that in 1989. For a list of treatments, see the treatment layouts in file trmte61.

本实验设置于与E060实验所用相同的B E004大样地（macroplots）中。划定了多组9m×9m的样方对，每对样方中的一个被随机分配为鸟类排除组（BEX），另一个为鸟类自由取食组（BAL），允许鸟类取食植被中的蝗虫。针对BEX组样方，以木质立柱搭建围框：四角各设置一根立柱，于立柱间距地面1m高处张紧重型铝丝；随后将网孔直径2.5cm的鸟类防护网覆盖于该围框之上，并以大量铁丝地钉将网体固定至地面。1989年，该批样方于7月15日搭建完成；1990年则调整为5月15日搭建，以探究初夏时节捕食作用的影响效应。8月15日至25日期间，移除防护网，对BEX组与BAL组样方内的蝗虫开展采样：采集所得的蝗虫被保存于70%乙醇溶液中，以待后续开展物种/属水平鉴定、个体计数及体重称量。本次蝗虫采样由两名操作人员使用捕蝶网完成。蝗虫采样结束后，随即开展植被采样工作：在每块9m×9m的样方内，划定三条0.1m×3m的样条，对植被进行刈割、物种分类、干燥处理及生物量称量。1990年，鸟类排除围栏搭建于5月15日，但其植被与蝗虫采样流程与1989年保持一致。如需获取处理组列表，请参阅文件trmte61中所载的处理布局方案。